Thienothiophene derivatives of the formula I R1-(A1)m-Z1-A-(Z2-A2)n-R2 I in which R1 and R2 are each H or an alkyl group having 1-12 C atoms, in which, furthermore, one or two non-adjacent CH2 groups can be replaced by O atoms, -CO- or -CH=CH- groups, or are each F, Cl, Br, CN, -COOR or -O-COR, A1 and A2 are each 1,4-phenylene, 1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, 1,3-dithiane-2,5-diyl, tetrahydropyran-2,5-diyl, pyridazine-3,6-diyl or the corresponding N-oxide, piperidine-1,4-diyl, 1,4-bicyclo[2.2.2]octylene or pyrimidine-2,5-diyl groups which are unsubstituted or substituted by one or two F, Cl or Br atoms and/or CN groups and/or CH3 groups, A is a group of the formula 1 or 2 which is unsubstituted or substituted by one or two Cl and/or Br atoms, Z1 and Z2 are each -CO-O-, -O-CO-, -CH2CH2-, -OCH2+13, -CH2O- or a single bond, R is an alkyl group having 1-10 C atoms, m is 1 or 2 and n is 0 or 1, and where m is 2, the two groups A1 can be identical or different, can be used as components of liquid crystalline phases.